Laura Shumaker first realized that Matthew was different from other toddlers when he was about a year old. During a group play date, other kids stayed busy exploring a variety of toys — and each other. Her son instead peered at the wheels of one toy the whole time. Although he had begun to talk like other 1-year-olds by then, Matthew mysteriously stopped soon thereafter.

Over the next few years, instead of answering questions, Matthew just repeated them. He focused intently on lights and other objects, yet had trouble looking his parents in the eye. The Shumakers, who live near San Francisco, took Matthew to doctor after doctor. They were anxious to figure out what was wrong. Eventually, when the boy was 5, an expert diagnosed Matthew with a brain disorder called autism.

“It was really hard because I truly didn’t know anyone else who had a child with autism,” Laura Shumaker says. (Her 2008 book — A Regular Guy: Growing Up with Autism — describes her family’s experience.)

Autism changes how the brain develops. As a result, affected kids often have trouble interacting with other people. They can struggle to communicate. They may repeat over and over the same behavior or action —such as rocking back and forth.

As a term, “autism” can refer to any of many different (but closely related) disabilities. Experts refer to the group as “autism spectrum disorders.”

Indeed, researchers use the word “spectrum” because autism’s symptoms can vary so much from one person to another. “It is such a broad-spectrum disorder: You can have a little bit of autism or a lot of autism,” Laura Shumaker says. “You can be a genius with autism but have no ability to interact with people. You can be non-verbal and very bright, or just like Matthew: He’s a nice, earnest guy who’s very quirky. Everyone’s different.”

Even though autism diagnoses are becoming more common, no one knows exactly why. “If you have 100 children in your school, you’re probably going to have one or two kids with autism,” says Zachary Warren. He directs a major autism institute known as TRIAD at Vanderbilt University in Nashville, Tenn. (TRIAD stands for Treatment and Research Institute for Autism Spectrum Disorders.) Warren says that many autistic kids struggle to do things that might come naturally to their others their age.

More than 20 years after Matthew’s diagnosis, researchers still don’t know what causes autism. Many scientists, however, are excited by new studies that suggest it can be spotted quite early in a child’s life. That’s important because other research shows that early treatment can make a big difference in reducing autism’s impacts.

Autism can be socially isolating

“Imagine waking up in the morning and wanting friends but just not being able to connect with them. Or being on the playground and being the last person that anybody wants to play with,” Laura Shumaker says. Kids with autism may have a hard time showing emotion. That makes it harder for others to know if they’re happy or sad. Similarly, children with autism have a hard time reading facial expressions. So they may not be able to figure out how others are feeling.

“Certainly, they enjoy things and are happy and get frustrated and are sad, just like all of us,” says Kathy Angkustsiri. “But they may not show it the same way.” Angkustsiri, a doctor and autism expert, studies child development and behavior at a research center. Located at the University of California, Davis, it’s called the MIND Institute. (MIND stands for Medical Investigation of Neurodevelopmental Disorders.) With autism impairing someone’s ability to show or read emotions, “You can see how that can get you into a lot of trouble as you get older and have to hold a job.” But even on the playground it can create social challenges, she says.

People with autism “don’t have the same ability to pick out the most important social cues,” Angkustsiri says. “It’s like the volume is just turned up all the way.” And if everything is at the same volume, she says, “you can’t sense the things that should stand out more.” Some scientists like to say that the brain is “wired differently” in people with autism. That means they often see, hear and feel the world in ways that the rest of us don’t.

Indeed, some children with autism can be extremely sensitive to loud noises, bright lights and even the textures of food. They may overreact to these sensations, yet still not respond when a parent calls their name.

When Matthew was young, Laura Shumaker says, he heard every noise. What’s more, “It was like a very loud noise all the time.” He’d be sitting in school trying to complete a workbook assignment. But “he couldn’t get the work done,” she says, because every noise was so distracting and bothersome.

When he was in second grade, someone pulled a fire alarm at school. For the next three months, Matthew refused to take his hands off of his ears. It’s one example of the exaggerated reactions that people with autism may have to events that upset them.

The Shumakers learned that Matthew couldn’t filter out sounds and sights like they could. So they adapted. When they drove in the car, for example, they learned that it was much easier for Matthew if no one talked. Piling on extra noise to the sounds and motion he was already sensing was simply too much for him.

Because people with autism can react to events and stimuli differently, many myths have cropped up about the disease, Laura Shumaker says. Many people, for instance, believe that children with autism are in their own world and don’t like to be touched. “Nothing could be farther from the truth for my son,” she says. “He’s hungry for friendship.”

Many possible causes

Scientists don’t know the exact cause of autism. But they are finding more and more clues to suggest that the varied brain disorders seen across the autism spectrum are due in part to the genes that babies inherit from their parents. A gene is a segment of DNA that codes for —or holds instructions for —producing a protein. Those proteins ultimately influence what an organism looks like and how it behaves.

If a child has autism, researchers know that the child’s siblings are more likely to have it too. So far, scientists have found hundreds of genes that might be linked to autism. But genes alone can’t fully explain why some kids develop autism and others don’t.

“The reality is that we don’t fully understand most of the causes of autism spectrum disorders,” says Warren at Vanderbilt University. “The reality is that there are likely many, many causes.”

Some researchers think that differences in a baby’s immune system —how well it fights off infections —might play a role. Angkustsiri says scientists are also looking at what happens during pregnancy, including the activity of a mother’s own immune system. Researchers hope to find out whether any changes before birth boost a baby’s risk of developing an autism spectrum disorder.

New research has added to the evidence that many changes in the brain may be linked to genetic problems. In one small study published March 27 in The New England Journal of Medicine, scientists looked at brain tissue from 11 autistic kids who had died. They focused on a type of tissue that normally is organized like a cake — with six different layers. In all but one of the youngsters, the scientists found patches here and there where some of the brain’s layers were totally disorganized. What’s more, the affected patches lacked specific genes that should have been there.

Because they weren’t, cells in the affected regions lacked the instructions needed to assemble properly. Among 11 kids without autism, the researchers saw similarly disorganized brain tissue in only one child.

The brain tissue that became disorganized is important for learning and memory, some studies suggest. It also has been linked to some of autism’s symptoms.

Such research suggests that autism might begin before birth, when this part of the brain begins organizing itself. The new study also supports the idea that treating autism early in life may rewire brain connections, allowing the circuitry to form detours around damaged areas.

One thing that doesn’t appear to trigger autism: childhood vaccines. Yet for years, many parents have heard rumors that these shots could be a cause.

In fact, there is no link between autism and vaccines, says Peter Jay Hotez. He’s a pediatrician and vaccine expert at Baylor College of Medicine in Houston. (He also directs the Sabin Vaccine Institute at Texas Children’s Hospital. The institute makes vaccines for people who live in poor countries.) “There’s no evidence that any of these vaccines are linked with autism,” Hotez argues.

Autism leads to so many complicated changes in the brain that it couldn’t be the result of giving kids a vaccine, he says. Plus, vaccines save lives. So parents who don’t let their kids get vaccines could be putting them at high risk for life-threatening diseases, such as measles and whooping cough.

For Hotez, understanding the real cause of autism is personal. He’s not only a pediatrician and a vaccine expert, but also the father of a 21-year-old with autism. Like the Shumakers, Hotez and his wife knew their daughter Rachel was different when she was very young.

Looking for early symptoms

In 2013, the U.S. government launched a big new project called BRAIN (short for Brain Research through Advancing Innovative Neurotechnologies). Researchers want to map out how the 86 billion neurons —the nerve cells that send signals zipping through the brain —interact. The project will likely take 10 years to finish. But scientists say it could help them understand how the “wiring” of neurons differs in people with autism.

That research could be important because autism can be hard to spot at first. “Typically, we can’t tell the difference at birth between a child who’s going to develop normally and a child who’s going to develop autism,” Angkustsiri says. “Some of the symptoms take time to develop.” Most kids aren’t diagnosed until they are 2 or 3. Many researchers, though, are trying to detect the disorder much earlier.

One group at the MIND Institute, in fact, has come up with a way to help tell whether the younger brother or sister of a child with autism also might have the disability. The test can spot signs in children as young as 6 months old. If a parent or other adult stands behind the child and repeatedly calls his or her name, does the child respond? If not, that could be a warning sign.

Researchers at Emory University in Atlanta have found that children who would later be diagnosed with autism spent less and less time, as babies, looking people in the eye. That behavior seemed to start as early as 2 to 6 months old. Babies who didn’t go on to develop autism, by contrast, paid more and more attention to a person’s eyes as they got older.

This difference is so subtle that people tend to miss it. But the Emory researchers used an experimental device to help them track each baby’s eye movements. It helped them spot this behavior very early. If this technology proves itself in bigger tests, it could give doctors another tool to help them diagnose the disorder.

Other studies are likewise finding early warning signs in the younger brothers and sisters of kids with autism. Some signs might point to their risk of developing autism too. Others might simply signal they may face some risk of other problems affecting brain development or behavior.

One recent study, for instance, suggests that doctors can begin to detect symptoms in children as young as 12 months old by looking at how they communicate, interact and move. That’s the conclusion of Sally Ozonoff of the MIND Institute and her colleagues.

They studied nearly 300 infants with older siblings who have autism. On March 6 in the Journal of the American Academy of Child and Adolescent Psychiatry, the researchers reported that 17 percent of the younger brothers and sisters eventually developed autism too. Another 28 percent showed early delays in their language, thinking skills and movement —and especially in making eye contact, pointing and communicating with unfamiliar people.

Those delays would easily have been missed if doctors had not been looking carefully, the study found.

Laura Shumaker finds such data “really exciting.” If a parent gets such early clues about a second child, she says, “You can say, ‘OK, I see something similar to my other child with autism, and I am going to get some intervention going right away.’”

And that early help, she says, can make a world of difference.

Power Words

autism spectrum disorders A set of developmental disorders that interfere with how certain parts of the brain develop. Affected regions of the brain control how people behave, interact and communicate with others and the world around them. Autism disorders can range from being very mild to being very severe. And even a fairly mild form can limit an individual’s ability to interact socially or communicate effectively.

gene A segment of DNA that contains the instructions for making a protein. Those proteins govern the behavior of a cell — or large groups of cells. Offspring inherit genes from their parents. Genes influence how an organism looks and behaves.

immune system The collection of cells and their responses that help the body fight off infections.

nerve cell orneuron Any of the impulse-conducting cells that make up the brain, spinal cord and nervous system. These specialized cells send information to other neurons in the form of electrical signals.

vaccine A biological mixture that resembles a disease-causing agent, given to help create immunity to a particular disease.